This invention relates to a disc player apparatus being provided with a disc clamper, particularly to improvement of a disc clamper for a digital disc player in which a disc is rotated with a relatively high speed.
Recently, an attempt is being made to put a digital disc player apparatus to a practical use for the purpose of a high fidelity and high density recording/playback operation of information. In a digital disc system, information such as an audio signal in PCM (Pulse Code Modulation) type digital form or a video signal is directly recorded on a disc. In such system, at the time of playback operation, digital signals recorded are picked up from the disc and thereafter they are demodulated. Here, there are some schemes of the recording/playback method for digital disc player apparatus. An optical recording/playback system or an electrostatic recording/playback system is a typical known scheme of the digital disc player. In these systems a constant line velocity (CLV) drive method is often used for recording and playing back digital information. In the CLV method, a pickup is linearly shifted with a constant speed along the radial direction of disk, and the rotational speed of disc is continuously varied with the shift of pickup so that the relative speed of the pickup in relation to a signal track of the disk is constant.
In a digital disc system, since a wide frequency range recording/playback operation is required, the rotation speed of a turntable for driving a disc is very high (e.g., 200 to 500 rpm.). During a period of time from the start (0 rpm.) to a given high speed rotation (500 rpm.), therefore, the disc is subjected to a large acceleration. Accordingly, if the disc is not steadily fixed to the turntable, the disc will slip over the turntable. Such slip will also be caused by the rotational speed change of the turntable during operation of the player.
To avoid the above slip, there is provided with a disc clamper for fixing a disc to the turntable. Namely, the digital disc player apparatus has a disk table driven by the rotational force of a motor and a clamper being supported by a certain support member. The disc is sandwiched between the disc table and the clamper and is steadily fixed to the turntable by the pressure effected therebetween. From this, it is required that the clamper is so supported that it can smoothly rotate with the rotation of the disc and that it can stably press the disc with a certain force. However, realization of the above requirement as to the supporting structure of said clamper and support member involves practical difficulties because of their complexity. Further, since such supporting structure is liable to impose fitful friction upon the turn table, it will cause to retard smooth rotation of the disk and unfavorably affect the quality of played back signals.